F212 Summary

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Molecules, Biodiversity, Food and Health
Biological Molecules
(a) describe how hydrogen bonding occurs between water molecules, and relate this, and other properties of
water, to the roles of water in living organisms
Water is a polar molecule. This is because the oxygen atom pulls the shared electrons towards it,
meaning that water is slightly negatively charged at the oxygen and positively charged at the
hydrogen ends, so they can form hydrogen bonds with each other. This are continuing breaking and
reforming, so the molecules can move around.
(b) describe, with the aid of diagrams, the structure of an amino acid

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A covalent peptide bond forms between the H of the amine group of one amino acid and the
OH from the carboxyl group of another. This is a condensation reaction where water is lost.
A water molecule is used to break the peptide bond.…read more

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(j) describe, with the aid of diagrams, the molecular structure of alphaglucose as an example of a
monosaccharide carbohydrate
(k) state the structural difference between alpha and betaglucose
In glucose the ­OH on carbon 1 is below the plane of the ring. In glucose it is above the chain of
the ring.…read more

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Made up of glucose joined by 1,4 bonds in a chain no branches.
Alternate glucose subunits are inverted
Forms straight chains which form fibres with hydrogen bonding between chains
The glycosidic bond can only be broken down by a cellulose enzyme, which herbivores
have, but humans do not
Forms plant cell walls
(n) describe, with the aid of diagrams, the structure of glycogen
Made up of glucose joined by 14 glycosidic bonds and also 16 glycosidic bonds which form
branches.…read more

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Phosphate may have carbohydrate attached forming glycolipids involved in cell signalling
Small, thin molecules that can fit into the lipid bilayer giving strength and stability
Used to form steroid hormones
(r) describe how to carry out chemical tests to identify the presence of the following molecules:
protein (biuret test),
Add biuret solution
If protein is present, turns from pale blue to lilac
Reducing sugars (Benedict's test),
Add Benedict's solution,
Heat to 80°C.…read more

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Nucleic acids
(a) state that deoxyribonucleic acid (DNA) is a polynucleotide, usually double stranded, made up of
nucleotides containing a nitrogenous base (adenine(A), thymine(T), cytosine(C) or guanine(G)), the sugar
deoxyribose and a phosphate group
(b) state that ribonucleic acid (RNA) is a polynucleotide, usually single stranded, made up of nucleotides
containing a nitrogenous base (adenine(A), uracil(U), cytosine(C) and guanine(G)), the sugar ribose and a
phosphate group. There are 3 types of RNA.…read more

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The mRNA attaches to a ribosome
Then tRNA molecules bring amino acids to the ribosome in the correct order, according to the base
sequence on the mRNA
The amino acids are joined together by peptide bonds to give a protein with a specific tertiary
If there is a mutation and the sequence of nucleotides is changed, the sequence of amino acids will
be changed.…read more

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If the pH change affects the charge on the amino acids at the active site, then the properties of
the active site change and the substrate can no longer bind
At high pH values, the ­COOH group will dissociate to become a charged ­COO group
Up to a certain point, increasing temperature will increase the rate of reaction, as there will be
more collisions between enzymes and the substrate, and more of these collisions will have the
required activation energy for the reaction to…read more

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As before, but keeping the temperature and the number of potato discs the same and
changing the concentration of hydrogen peroxide in each test tube
(f) explain the effects of competitive and noncompetitive inhibitors on the rate of enzymecontrolled reactions,
with reference to both reversible and nonreversible inhibitors
Competitive inhibitor molecules
Have a similar shape to that of the substrate molecule.
This means that they occupy the active site, forming enzymeinhibitor complexes.…read more

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Food & Health
Diet & Food Production
(a) define the term balanced diet
A diet that contains all the nutrients of the nutrients requires for health and growth in the correct
(b) explain how consumption of an unbalanced diet can lead to malnutrition, with reference to obesity
Malnutrition is caused by an unbalanced diet.
Obesity is called by consuming too much energy and the excess energy is deposited as fat in the
adipose tissues.…read more


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